Deserts（沙漠）are changing. Sometimes they grow big. Sometimes they get small. The world's biggest desert, the Sahara, is in Africa（非洲）. Now, the Sahara Desert is growing fast.
Why is the Sahara growing? In some places, people farm too much. In other places, animals eat all the grass. And also people cut down too many trees. All these make the soil weak. Weak soil lets the deserts grow. This is a big problem（问题）because people cannot grow plants in the desert. People cannot build houses, hospitals, or schools in the desert. So people must leave their homes. They must live somewhere else.
How can we change it? Let's plant more trees. We can farm less. These make the soil strong. Maybe the Sahara will stop growing. All of the people from different countries should work together to solve the problem.
